Marketing can be so frustrating sometimes. You know people want what you have, they're aware of what you have, but you don't hear from them. I was talking to one of our customers and he told me, he's just so busy. He laughed and said all of the things he needs to do is like a wheel, and when it stops and our name is there, he'll do something.
I like that analogy. So the trick is to get more spots on the wheel so when it does stop, you have a good chance of getting that attention. But be a nuisance and you just get taken off the wheel.
One good trick is a news summary delivered once a week or once a month (depending upon the desires of your market). But if you're going to do this, do not make them jump through hoops to get the information. For instance I get a weekly blast from eWeek. Some great third party white papers. So I click on the link, get a teaser for the paper, and then hit a registration wall. Now let's think about this. You know who am I. You sent me an email. Yet when I click on the link, it's total amnesia. Here's a clue, transmit my email address with the link, pull my information, give me the opportunity to change it, then get the paper. This ain't rocket science folks.